Psychology Unit 2

Sensation

Detecting physical energy with the sense organs, such as the eyes, ears, skin, nose, and tongue.

Perception

The brain's interpretation of that raw sensory information.

Illusion

A case in which the way a stimulus is perceived does not match its physical reality

Why do illusions matter?

They show perception involves processing rather than direct contact with the world. The way the system breaks down reveals the work it normally does.

Transduction

The conversion of an external stimulus into a neural signal.

Sensory Receptors

Specialized cells that convert one kind of external energy into a neural signal. Each type signals only on or off, and they are the mind's only contact with the outside world.

Sensory Adaptation

Sensory neurons adjust their sensitivity based on recent stimulus history, responding strongly to change and weakly to constant input. Examples include a strong smell that “fades”, adjusting to a dark room, and color afterimages.

Aftereffect

An opposing distortion that follows adaptation. Staring at motion in one direction makes a still image appear to drift the other way

Frequency of wavelength in sound

Pitch

Frequency of wavelength in light

Color (hue)

Amplitude of wavelength in sound

Loudness

Amplitude of wavelength in light

Brightness

Psychophysics

The study of how sensations, which are psychological events, correspond to physical events in the world

Absolute threshold

The lowest level of a stimulus the nervous system can detect 50% of the time. It compares something with nothing.

Why 50% for absolute threshhold?

Detection is not all or nothing, so the threshold is defined as the level detected half the time. Under ideal conditions people can detect a candle flame 30 miles away or a teaspoon of sugar in a gallon of water.

Just noticeable difference (JND)

The smallest change in intensity that can be detected, again 50% of the time. It compares something with something

Weber’s Law

The stronger the stimulus, the bigger the change needed to detect it. What matters is the proportion, not the raw amount

Consequence

Doubling the physical intensity of a light does not double perceived brightness. Each noticeable step requires a larger physical change than the step before it, so our senses compress very large physical ranges.

Signal

What you are trying to detect.

Noise

Competing stimuli that interfere with detecting it

Signal-to-noise ratio

Difficulty depends on the strength of the signal relative to the noise

Stimulus present, you respond “yes”

Hit (true positive)

Stimulus present, you respond “no”

Miss (false negative)

Stimulus absent, you respond “yes”

False alarm (false positive)

Stimulus absent, you respond “no”

Correct rejection (true negative)

Response criterion

How liberal or conservative a person is about saying yes. Hits and correct rejections cannot both be maximized, so shifting the criterion trades one error for the other. Saying yes more readily reduces misses but increases false alarms.

Application beyond perception

For a doctor screening for cancer, a liberal criterion catches nearly every real case but subjects many healthy people to stress and unnecessary procedures, while a conservative criterion avoids that cost but leaves some people untreated

Attention

The selective filter that determines which part of an overwhelming sensory input gets processed deeply, often called the spotlight of experience.

Dichotic listening

Different messages play in each ear and people report only the attended ear, shows that attention works somewhat like a filter

Cocktail party effect

Your own name breaks through from the unattended channel, shows that unattended information is still processed to some degree

Inattentional blindness

Unattended stimuli are missed as though they were not there, shows that attention is more limited than people assume

Change blindness

People fail to detect large changes in a visual scene, shows that scenes are not held in detail moment to moment

Bottom-up processing

Building a representation from parts and basic features, starting with the raw sensory data.

Top-down processing

Processing influenced by previous experience, knowledge, and expectation, starting with meaning and using it to interpret the stimulus

Why is top-down processing hard to switch off

Once an ambiguous image or a degraded recording has been identified, it cannot be experienced the way it was before

Perceptual set

A readiness to perceive in a particular way, formed when expectations influence perception. Students shown a series of faces first tend to see an ambiguous figure as a face, while students shown bodies tend to see a body

Pupil

Where light enters

Iris

Colored, controls size of pupil

Cornea

Covers eye, focuses light

Lens

Covers eye, changes shape to focus near or far, bends light

Accommodation

When the lens changes shape from near to far

Retina

Back of the eye, converts light into neural signals

Fovea

Central region of eye, has lots of cones and is responsible for acuity

Optic Nerve

Carries signals back to brain

Blind Spot

Where optic nerve exits the retina

Acuity

Sharpness of vision

Saccades

Small rapid eye movements that place the fovea on a new location

Myopia (Nearisghtedness)

When the eye is too long)

Hyperopia (Farsightnedness)

When the eye is too short

Rods

Work in low light, are not color sensitive, carry less fine detail, sit mostly outside fovea, more plentiful

Cones

Need more light, are color sensitive, carry fine detail, concentrated in fovea, less plentiful

What Pathway (Ventral Stream)

identifies objects, underside of temporal lobe

Where pathway (dorsal stream)

Location and movement, up to parietal lobe

Hue

Color of light

Trichromatic Theory

Color vision is based on 3 colors (blue, green, and red) because we have three cones tuned into short, medium, and long wavelengths. Does not explain afterimages

Opponent Process Theory

Color is coded in 3 opposing pairs (red & green, blue & yellow, black & white), adapting to one member produces afterimage

Color Blindness

Reduced color discrimination, usually from loss of one or more cone types

Binocular Cues

Requires two eyes

Binocular Disparity

Each eye receives a slightly different image, 3D films

Convergence

Eyes turn inward for near objects and the brain tracks how much

Relative size (monocular cue)

Distant objects produce smaller images

Texture gradient (monocular cue)

Texture is finer and less distinct with distance

Interposition (monocular cue)

Nearer objects block more distant ones

Linear perspective (monocular cue)

Parallel lines appear to converge with distance

Height in plane (monocular cue)

More distant objects appear higher in the visual field

Light and shadow (monocular cue)

Shading indicates 3D form

Motion parallax (monocular cue)

Nearer objects sweep past more quickly than distant ones

Perceptual Constancy

We perceive objects as constant even though the sensations arising from them change, depends on depth cues

Learning

relatively permanent change in behavior or thoughts as a result of experience, adaptive, aids survival

Non-associate learning

Responding to a single stimulus, includes habituation and sensitization

Associative learning

Connecting 2+ stimuli or events that occur together, includes conditioning

Complex cognitive learning

Learning without direct reinforcement or trial and error, includes observational and insight learning

Habituation

Responding less strongly over time to a repeated stimulus, usually a neutral one, like background noise in a restaurant

Sensitization

Responding more strongly over time to a repeated stimulus, usually one that is dangerous or irritating, such as a sibling poking you repeatedly

Classical Conditioning

A form of learning in which two stimuli are repeatedly paired. A neutral stimulus is paired with one that already elicits an automatic response, until the neutral stimulus triggers that response on its own

Acquisition

When the CS is paired with the US until the CS produces the CR, the learning phase

Extinction

The CS appears alone and the CR weakens, then disappears, not the same as forgetting

Spontaneous Recovery

After a delay, the extinguished CR. reappears when the CS is presented again, response is inhibited but not erased

Renewal effect

A response extinguished in one context returns in the original setting, shows suppression and not erasure

Generalization

Responding to stimuli that resemble the CS, learning is not tied to one exact stimulus

Discrimination

Responding to one stimulus but not to different ones, prevents overgeneralization

Blocking

A prior association with one CS prevents learning about a new stimulus, second stimulus adds no predictive value

Preparedness

A biological predisposition to learn some associations faster, fears of heights/snakes/spiders have survival value

Taste aversion conditioning

Associating nausea with a food, helps us avoid food that is spoiled or poisonous, example of preparedness

Fear conditioning

Negative associations can be learned extremely rapidly through a very fearful and traumatic event

Chronic drug use

Cues present when drug taken like room or smell become CS and body produces responses that prepare for drug and reduce its impact, raises tolerance and leads to higher doses, doing same dose in different environment can lead to overdose

Advertising

Pairs products with celebrities and pleasant settings

Operant conditioning

A change in voluntary behaviors as a result of its consequences

Thorndike’s Law of Effect

Behavior is a function of its consequences

Skinner box

Apparatus that controls the consequences of a behavior and records how often and how quickly it occurs

Discriminative stimulus

Any stimulus that signals the presence of reinforcement, which puts the behavior under stimulus control

Reinforcement

Increases the likelihood that a behavior is repeated

Punishment

Decreases the likelihood a behavior is repeated

Continuous reinforcement

Rewarded every time, faster acquisition and faster extinction

Partial reinforcement

Rewarded only some of the time, slower acquisition and slower extinction

Fixed ratio

Consistent number of responses, a bonus for every five items sold

Variable ratio

Average number of responses, a slot machine

Fixed interval

Consistent time, a weekly quiz

Variable interval

Average time, pop quizzes

Quantitative Law of Effect

The effect of reinforcing one behavior depends on how much reinforcement its alternatives earn, a given reinforcer is weaker in an environment full of other rewards